Purpose of Disconnecting The Neutral 2

[Energyfit24381]

Good afternoon,

Im working on a distributed generation application where i will need to disconnect the neutral when switching from utility power to generator power. We have a bonded neutral to ground source (utilty transformer NTRL will be bonded to ground inside of the switchgear it feeds) and the back ATS controlling the gens will be grounded there as well while the gens are equipped with NGR’s that tie into that same common geound. Just looking for help understanding the purpose of having to disconnect the neutral in the event of a utility outage and switching to generator backup.

“If my critics seen me walk on water they would say its because i cant swim”

- M.T.-

 

[waross]

The ATS will work, that part has been vetted. We are not doing a traditional tranformer/Main intercept but we do have CT/PT’s on the Mains (being fed by transformer) to sense loss of utility. That information will travel to the gen controllers to start the gen startup process. Upon that condition the mains will open, gens will start and synch (the “G” breaker will be open during that sequence) and when controller sees all gens on line the “G” breaker will close feeding the normally closed “M” breaker which will then back feed into the main swgr breaker as shown to feed the loads. Again the Main Swgr breaker will remain open during this condition which @waross is island mode.

We will be exporting as well though.

Those statements are contradictory and mutually exclusive.
AND
Your sketch is contradictory of both statements.
BUT
If the neutral grounding is shown correctly in your sketch, you will need a very expensive transfer 4 pole transfer switch to safely and properly switch the neutrals.
AND
You should probably lose the NGRs.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!